A Review of Horticulturally Desirable Characters in Kalanchoe (Crassulaceae subfam. Kalanchooideae): Variable and Deviating Vegetative and Reproductive Morphologies Useful in Breeding Programmes

Abstract: Variation and deviations in reproductive morphological characters, especially in flower colour and the occurrence of single vs double flowers, in species and hybrids from which cultivars have been selected in Kalanchoe (Crassulaceae subfam. Kalanchooideae) have given rise to the establishment of a multi-million € horticultural enterprise based on, inter alia, K. blossfeldiana and hybrid material of which it is one parent. Kalanchoes are mostly made available for the trade in material grown indoors. More recently, the breeding of kalanchoes as a source of long-lasting cut flowers, as well as incorporating vegetative, not only reproductive, variation into hybrid offspring have received increasing attention. Vegetative characters of horticultural interest are mostly those of the leaves (colour, maculation, shape). Especially given the ease with which kalanchoes, including nothospecies and cultivars, respond to cultivation outdoors in places where water for irrigation is at a premium, material other than K. blossfeldiana-derived cultivars has recently seen an upsurge in popularity. In the family Crassulaceae as a whole, deviations in leaf morphology, such as surface carunculations, is best known among representatives of other crassuloid genera, including Echeveria (Crassulaceae subfam. Sempervivoideae). Such deviations, too, have given rise to the selection and description of numerous horticulturally popular cultivars, for example derived from E. gibbiflora. The development of leaf carunculations is for the first time reported from K. neglecta and K. nyikae, which are endemic to southern and East Africa, respectively. We provide a review of variable and deviating vegetative and reproductive morphologies in Kalanchoe species, nothospecies, and cultivars popular among plant breeders.